St Margaret's Hope Hydrographic Analysis and Bathymetric Reporting Scottish Sea Farms

Assignment Number: A30530- S12 Document Number: A-30530-S12-REPT-001

Xodus Aurora 8 Garson Place KW16 3EE UK

T +44 (0)1856 851451 E info@xodusgroup. com www. xodusgroup. com

Xodus Aurora

Table of Contents

1 INTRODUCTION 4

2 SCOPE OF WORK 5

2.1 Methodology 5 2.1.1 Site survey 5 2.1.2 ADCP hydrographic meter 6 2.1.3 Meteorological station 7

3 SURVEY RESULTS 8

3.1 Bathymetric description of site 8 3.2 Hydrographic data 10

4 HYDROGRAPHIC SUMMARY STATISTIC AND DATA PLOTS 11

4.1 Current meter data summary statistics and plots 12

5 REFERENCES 15

APPENDIX A ADCP SPECIFICATIONS 16

APPENDIX B PITCH, ROLL AND HEADING DATA 22

St Margarets Hope Hydrographic Report - Hydrographic Analysis and Bathymetric Reporting Assignment Number: A30530- S12 Document Number: A-30530- S12- REPT- 001 iii 1 INTRODUCTION

A hydrographic and bathymetric survey was undertaken for a proposed salmon farm site at St Margaret’ s Hope, , Orkney. The survey was undertaken by Xodus Aurora on behalf of Scottish Sea Farms (SSF). The proposed St Margaret’ s Hope salmon farm will consist of 16 circular cages with an 80 m circumference. The salmon farm cages will be arranged in 2 symmetrical lines of 8 cages, arranged in a west to east direction. The site centre of the cage group will be 58° 50.137 N 02° 58.915 W (343417E 994657N). The proposed site is located in , approximately 211 m north of the nearest shoreline of South Ronaldsay. The proposed site is sheltered by South Ronaldsay to the south, to the east and Hunda to the north, but St Margaret’s Hope is open to Scapa Flow to the west. The closest land reaches a height of 60 m at Hoxa Hill to the south (see Figure 1.1). Figure 1.1 Location of the proposed salmon farm site at St Margaret’s Hope, South Ronaldsay

St Margarets Hope Hydrographic Report - Hydrographic Analysis and Bathymetric Reporting Assignment Number: A30530- S12 Document Number: A-30530- S12- REPT- 001 4 2 SCOPE OF WORK This report summarises the data collected by current meter measurements and depth position fixing at the proposed St Margaret’ s Hope salmon farm site. The data presented in this report are submitted in support of an application for the consent to discharge from a marine cage fish farm, under the Water Environment ( Controlled Activities) ( ) Regulations 2005, as per SEPA requirements ( Annex VIII of SEPA Fish Farm Manual).

The following surveys were conducted at the St Margaret’ s Hope site. All data collected are contained within this report:

Hydrographic survey 14th April to 3rd May 2011 inclusive; and

Meteorological survey 13th April to 4th May 2011 inclusive; and

Bathymetric survey 14th of April 2011.

2.1 Methodology

2.1.1 Site survey

A site survey for the proposed St Margaret’s Hope salmon farm site was undertaken on 14th of April 2011 using a depth sounder as per SEPA requirements and in accordance with the Aurora Standard Operating Procedure SOP), AE-SOP-005. All depth-sounding positions were determined by Global Positioning System ( GPS) ( see Figure 3.1). The following information was collected on site:

Five depth readings at each location;

Time and date of readings; and

Position fix of reading. All depths were corrected to chart datum using St. Mary's (Scapa Flow) as the secondary port for tidal correction purposes. Both time and tidal height at 5 minute intervals over the survey period were extracted for St. Mary's from the Admiralty TOTALTIDE software. Tidal corrections per sounding were achieved by subtracting the interpolation of the tide height increments, with respect to the survey time, from the sounding depth. Interpolation was achieved using EXCEL software. All data were then converted from WGS84 Lat/Long to OSGB36 National Grid using Grid Inquest (version 5.02). Results of the bathymetric survey are presented in Section 3 of this report.

St Margarets Hope Hydrographic Report - Hydrographic Analysis and Bathymetric Reporting Assignment Number: A30530- S12 Document Number: A-30530- S12- REPT- 001 5 2.1.2 ADCP hydrographic meter

2.1.2.1 Current meter deployment

The hydrographic survey was undertaken between the 14th of April to the 3rd of May 2011 inclusive, using an RDI 600 kHz Workhorse Acoustic Doppler Current Meter ( ADCP). The current meter specifications are provided in Appendix A. The ADCP was deployed at position 58° 50.134 N 02° 58.900 W ( 343432 E 994650 N) as determined by GPS (see Figure 3.1). The ADCP was set up before deployment to take current readings at every 0.5 m increment through the water column with the lowest reading at 2.06 m above the seabed ( see Figure A.1 in Appendix A). ADCP set-up including details on blanking distances are provided in Appendix A. Pre-deployment checks of the meter were carried out by Xodus Aurora. The current meter was held in position at the seabed using a weighted, stainless steel frame and gimble. The mooring was positioned where topographic features would not cause spurious data collection for the salmon farm site. The current meter was deployed in a mean water depth of 18.5 m MD within 150 m of the proposed cage group centre (Figure 2.1). The current meter was preset to collect current speed, current direction and water depth at 20- minute intervals. The ADCP current meter remained at the proposed St Margaret’s Hope salmon farm site for a period of 19 days. This was enough to ensure there was a period of 15 days satisfactory data and the hydrographic survey would not have to be repeated. 2.1.2.2 Current meter retrieval

A preliminarily assessment of the data was undertaken when the ADCP current meter was retrieved and it was confirmed that were no anomalies or data gaps present. All raw data files were successfully downloaded by Xodus Aurora and analysis of the data to current SEPA requirements was undertaken by Xodus Aurora. Analysis has been undertaken of pitch, roll and heading readings for the current meter. During this period of the current meter’s deployment there was only a minor alteration in the pitch, roll and heading by <1º. This variation is not deemed to have an effect on the data analysed ( see Appendix B). 2.1.2.3 Current meter analysis

Analysis of the 15 day hydrographic data was carried out using data collected between the 15th to the 30th April 2011. This ensured data analysis was based around a 15-day cycle ( half-lunar period) ( see Section 3.2). Records 45 to 1125 were taken for analysis purposes. This data was used for analysis purposes as it represented the most stable data with only minor alterations in pitch, roll and heading. Analysis of the hydrographic data to current SEPA requirements was undertaken by Xodus Aurora. Xodus Aurora Standard Operating Procedure AE-SOP-010 was followed for the interpretation of the hydrographic data, results of which are presented in Section 3 of this report.

St Margarets Hope Hydrographic Report - Hydrographic Analysis and Bathymetric Reporting Assignment Number: A30530- S12 Document Number: A-30530- S12- REPT- 001 6 2.1.3 Meteorological station

Wind conditions at the proposed St Margaret’ s Hope site were recorded at Sandy Hill ( 58°46’9.83”N, 2°57’3.42W 345100 E 987256 N) between the 13th April to 4th of May 2011, inclusive. The weather station is located approximately 7.55 km from St Margaret’ s Hope, in South Ronaldsay. Sandy Hill weather station was used for analyses purposes as the closer Barrel of Butter Weather Station developed a fault on 14 April. Sandy Hill is a representative weather station as it is exposed to the same weather conditions as the proposed St Margaret’ s Hope site. Typically recording the same or higher wind speeds than Barrel of Butter Weather Station. This can be seen on the live weather display from Orkney harbours or from historic data (see www.orkneyharbours. com). The meteorological data ( Figure 2.1) for the period of the 13th April to 4th of May 2011 were taken for analysis to coincide with the period of hydrographic analysis. On analysis it was confirmed that at least 3 consecutive days presented wind speeds of less than 10 m/s ( 19.3 knots). Results of the survey are contained in the CD accompanying this report. Figure 2.1 Daily wind speed and direction at the Sandy Hill Weather Station, South Ronaldsay. 13/04/2011 until 04/05/2011)

St Margarets Hope Hydrographic Report - Hydrographic Analysis and Bathymetric Reporting Assignment Number: A30530- S12 Document Number: A-30530- S12- REPT- 001 7 3 SURVEY RESULTS

3.1 Bathymetric description of site

Bathymetric data have been extracted from chart data which extends to cover a 1 km square plot area and will be used for modelling purposes. These data have been supplemented by the following site survey data collected at the site (see Table 3.1 and Section 2.1.1). Sounding depths were converted to Chart Datum using Standard Port of Wick and Secondary Port of St. Mary's. Data was collected from the following:

Depths in close proximity to the cage corners; and

Additional depth measurements in cardinal directions from the cage corners.

Figure 3.1 St Margaret’ s Hope site survey and bathymetric plot

St Margarets Hope Hydrographic Report - Hydrographic Analysis and Bathymetric Reporting Assignment Number: A30530- S12 Document Number: A-30530- S12- REPT- 001 8

3.2 Hydrographic data

Hydrographic data for the proposed St Margaret’ s Hope salmon farm site are plotted in the following sections and provided electronically with the accompanying CD. For data plotting, three water depths were selected ( see Section 4) as charted depths were more than 15 m:

Seabed (2.06 m above the seabed);

Net depth and (8.56 m above the seabed)

Sea surface ( 11.56 m above seabed); The ADCP records direction as ° magnetic north. On retrieval of data, the directions relating to the plotted water depths were converted to ° Grid north. The World Magnetic Model from British Geological Survey was used to obtain the declination for St Margaret’s Hope on the date of the survey. SEPA HGdata_analysis_v7.xls spreadsheet was used to obtain the difference between true north and grid north for St Margaret’s Hope. This value was added to the declination to obtain the difference between magnetic north and grid north ( the grid magnetic angle). This value is used to correct the raw uncorrected hydrographic data to ° grid north. A summary of the magnetic variation allowance is provided in Table 3.2 detailing the data inputs and outputs from the World Magnetic Model. Table 3.2 Magnetic variation allowances

Parameter Reading Input Date of survey (decimal years) 2011.4 Current meter national Latitude Longitude 58° 50.134 N 02° 58.900 W Current meter national grid reference 343432 E 994650 N Output Declination: - 3.99 Grid Magnetic Angle - 3.15 Convergence: - 0.84

St Margarets Hope Hydrographic Report - Hydrographic Analysis and Bathymetric Reporting Assignment Number: A30530- S12 Document Number: A-30530- S12- REPT- 001 10 4 HYDROGRAPHIC SUMMARY STATISTIC AND DATA PLOTS

St Margarets Hope Hydrographic Report - Hydrographic Analysis and Bathymetric Reporting Assignment Number: A30530- S12 Document Number: A-30530- S12- REPT- 001 11 06 Deg- 2.1 15(3.

840 GMA: -

Figure 4. 990convergence: - 0.

38declination: - 3. and plots 994650mNMax: 20.

ID :343432mE summary statistics Current meter

s Hope meter data St Margaret’

seabed at

1 Current m above

4. sHopeCurrent measurementof15/4/ :

St Margaret’ 18. 53Period

G)Mean: seabed at 15( Deg-

GMA: -3. m above 0.840

3.990convergence: -

8.56 20. 38declination: -

343432mE 994650mNMax:

4.2 meter ID :

Figure Number:A30530- S12 GMA:840 3.-15(

Reporting Assignment 990convergence: - 0.

38declination: - 3. and Bathymetric 994650mNMax: 20.

ID :343432mE

Hydrographic Analysis Current meter

001 14

Hydrographic Report - S12- REPT-

A-30530-

Margarets Hope Document Number:

St 5 REFERENCES

Xodus Aurora Standard Operating Procedure AE-SOP-010 Hydrographic Data Interpretation.

Xodus Aurora Standard Operating Procedure AE-SOP-010 Interpretation and Reporting of Hydrographic and Bathymetric for Salmon Farm SEPA Consent Application.

Orkney Islands Council Marine Services webpage, Weather and Tides (2011) http://www.orkneyharbours.com/weather.asp

St Margarets Hope Hydrographic Report - Hydrographic Analysis and Bathymetric Reporting Assignment Number: A30530- S12 Document Number: A-30530- S12- REPT- 001 15 APPENDIX A ADCP SPECIFICATIONS

The following table provides specification information for the RDI 600 kHz Workhorse Acoustic Doppler Current Meter (ADCP). Table A.1 ADCP equipment specifications

Parameter Accuracy Precision Resolution Range Speed ( cm/s) ± 0.25% +2 mm/sec < 1 0.1 2,000 max Direction ± 2.0° ± 0.5° 0.01 0360 - Pressure ( dB) n/a n/a n/a n/a Tilt/Roll ± 0.5 ± 0.5 0.01 ± 15 Temperature Not Known 0.4 0.01 - 5 to 45

The following table provides specification information for the RDI 600 kHz Workhorse Acoustic Doppler Current Meter (ADCP) set up parameters. Table A.2 ADCP set up parameters

Parameter Setting System Frequency ( kHz) 614.4 Ping interval (mins) 00:03 Ping/Ens 500 First Ensemble 11/04/14 First Ensemble 09:39:37.33 Ensemble interval ( seconds) 1200 Bin size (m) 0.5 Blanking distance ( m) 2.06 1st Bin Range 1.61 Bins 59 Transducer 4 Beam Janus Beam Angle (Degrees) 20

St Margarets Hope Hydrographic Report - Hydrographic Analysis and Bathymetric Reporting Assignment Number: A30530- S12 Document Number: A-30530- S12- REPT- 001 16 Figure A.1 ADCP hydrographic meter set-up parameters for blanking

Bin 1 0.5 m) Mid bin 0.25 m)

Blanking Total Lowest Distance Blanking Reading 1st bin range above distance 2.06m) 1.61 m) Transducer 1.81m) 1.11 m)

ADCP Height of Transducer Weighted Stainless above seabed steel frame and 0.70 m) gimbal

St Margarets Hope Hydrographic Report - Hydrographic Analysis and Bathymetric Reporting Assignment Number: A30530- S12 Document Number: A-30530- S12- REPT- 001 17 Figure A.2 ADCP Function and Parameters settings

St Margarets Hope Hydrographic Report - Hydrographic Analysis and Bathymetric Reporting Assignment Number: A30530- S12 Document Number: A-30530- S12- REPT- 001 18 St Margarets Hope Hydrographic Report - Hydrographic Analysis and Bathymetric Reporting Assignment Number: A30530- S12 Document Number: A-30530- S12- REPT- 001 19 St Margarets Hope Hydrographic Report - Hydrographic Analysis and Bathymetric Reporting Assignment Number: A30530- S12 Document Number: A-30530- S12- REPT- 001 20 St Margarets Hope Hydrographic Report - Hydrographic Analysis and Bathymetric Reporting Assignment Number: A30530- S12 Document Number: A-30530- S12- REPT- 001 21 BAPPENDIX